Research On The Quality Control Technology Of C20～C30 High-performance Concrete

In the construction of infrastructure, low strength concrete is still the main application, how to effectively control the quality of low intensity C20-C30 high performance concrete is still a focus issue attention by today’s engineering and technical personnel. In this paper, quick test technology of the effective water-cement ratio of new mixed C20-C30 high performance concrete were researched, and analyzes the impact of test time, the type and content of admixtures on the test results; Referring to the national standard strength-measuring curve of the concrete, C20-C30 high performance concrete local standards strength curve were studied interior, initially built C20-C30 high performance concrete comprehensive quality control system.The main conclusions are as follows:(1) Washing sieving test results show that:With the increase of test time, test the value of fresh concrete water-cement ratio presented progressively decreasing trend, in the concrete mixing with water after about 5-7min measured value and the theoretical value closest. When mineral admixtures content not exceeding 10%, regardless of fly ash, slag is single mixed or admixed, the measured water-cement ratio are highly consistent with the design water-cement ratio; When the mineral admixtures content exceeds 20%, the test results when fly ash and slag complex mixed is closer to the theoretical value than a single fly ash (or slag).(2) Applicability analysis shows that:When presumption the strength of the C20-C30 high performance concrete in Hunan Province with the Ultrasound-Rebound comprehensive method unified strength curve, the relatively error are large than regulatory requirements by nearly 25 percent, far beyond the extent permitted of the norm. So Ultrasonic-Rebound combined method unified strength curve is not applicable to high performance concrete strength testing.(3) Establishment rebound-strength a variable regression equations of C20～C30 high performance concrete, among them the linear regression equation is fcu=1.0204R+2.7410 (the total sample n=449, the mean relative error δ=7.69%, the mean relative standard error er=10.31%, the correlation coefficient r=0.8848), the power function regression equation is fcu=1.2528R0.9619(n=449,δ=7.62%, er =10.41%, r=0.8842), the exponential regression equation is fcu=15.4635e0.0255R (n=449,δ=7.83%,er=10.54%, r=0.8594).(4) Establishment the ultrasound-rebound-strength binary regression equation of C20-C30 high performance concrete, where the linear regression equation is fcu=46.6889v+0.7309R-165.57(n=449,δ=7.39%, er=9.67%, r=0.8982),the power function regression equation is fcu=0.0097R0.7056 v4.3023 (n=449,δ=7.43%, er=9.89%,r=0.8998).(5) The accuracy comparative analysis of each equation shows that:The power function strength curve established by binary regression analysis has the largest correlation coefficient, and the average relative error and the relative standard deviation is relatively small, for the conditional construction units and quality control department, recommend preferred use the comprehensive measure of the power function regression formula to the concrete quality testing and acceptance.(6) Combines the research of the effective water-cement ratio testing technology and concrete strength curve of high performance concrete, initially built C20-C30 high performance concrete comprehensive quality control system; The system contains the advance control, the in-process control and the post-action control, can monitored the quality of high performance concrete timely and effective.